Laguerre-Gaussian Laser Beam Shaping for Control of Optical Angular Momentum in Ultrafast Laser Spectroscopy of Quantum Materials

The project's main goal is to develop an optical system for generating and controlling laser pulses with desired states of Optical Angular Momentum (OAM) needed for experiments that will study spin states in quantum materials. A beam of light has a linear momentum which depends on the spatial distribution of an Optical Field (E) where E represents a specific electric field distribution which in this case is a Gaussian distribution. The specific OAM that’s being desired is modeled using a helical mode in which the wavefront of the momentum is shaped like a helix.<br/>The first step was to use MathCAD Prime to model the 2D patterns or filter needed to transform the Gaussian beam into the desired OAM wavefront. The point of this is to control the energy distribution of the laser wavefront so when it interacts with a material so that we can model the interaction of electron spins in the material with the OAM wave using quantum mechanics.<br/>Second, we implemented the 2D patterns calculated using Mathcad on a spatial light modulator (SLM). An ultrafast laser beam was expanded to a diameter of 3 cm and passed through the SLM resulting in an OAM that could be observed by interfering the OAM beam with a plane wave beam split off from the original laser beam. Finally, the patterns generated in the experiment were compared with the modeled patterns and the results shows promise for future use in experiments of spin states in materials.<br/>Future work includes refining the model used to generate the patterns on the SLM and implementing the system in the study of quantum materials which is the subject of my PhD thesis.